Fillers are routinely used by polymer and plastic industry to reduce the cost of end products and to enhance some desired properties, such as physical and mechanical properties. However, conventional filler materials can be costly and therefore need to be processed in an efficient manner, and conventional inorganic fillers, such as aluminium trihydroxide and the like may pose environment risks when used as polymer fillers.
Formulation of biocomposites has been an attractive endeavor for researchers in the last decade. There are several advantages, either environmental or economical, of using biocomposites over ordinary composites, especially those based on thermoplastics matrices, for various applications such as structural and food packaging. The biodegradability feature of such composites offers a solution for the problem of municipal waste management. Besides the biodegradability of polymers filled with biomaterials, the availability of these fillers, normally of agricultural residue origin, at very low cost levels makes the production of these composites economically feasible.
Several biocomposite systems of thermoplastic matrices and bio-fillers have been reported in the literature, wherein various bio-fillers, such as wheat straw, corncob, rice husk, and sugarcane bagasse were incorporated with polymer matrices, such as polypropylene, high-density polyethylene (HDPE), low-density polyethylene, and polyvinyl chloride. From an economic point of view, incorporating a cost-effective filler in a polymer will only be feasible if it does not drastically alter the main matrix-resin characteristics, such as mechanical properties.
Saudi Arabia is well recognized for its palm trees (Phoenix dactylifera L.). In addition, Saudi Arabia is among the largest world producers of date fruit, 4700,000 MT per year. On the consumption of date fruit as a main daily meal in almost each Saudi dwelling, date pits are usually discarded as materials with no use or value. Nevertheless, these presumably designated waste materials, i.e., date pits, contain important constituents such as oils (up to 10%), minerals (considerably rich in potassium), and fibers (46.4%) that may be utilized for specific purposes.
Ghazanfari et al. (“Thermal and Mechanical Properties of Blends and Composites from HDPE and Date Pits Particles”, Journal of Composite Materials, 42(1) (2008); pp. 77-89) disclose formulating polymer-date pits composites based on HDPE as the hosting polymer, and conclude that incorporating date pit flour with HDPE tends to decrease the melt flow index (MFI), and at the same time increase the thermal conductivity of the resulting composites. The date pits investigated by Ghazanfari et al. are of the Abdoulahi cultivar, which demonstrate reductions in tensile strength as compared to non-composited (neat) polymer, on increasing weight percentages of date pit flour in the composites.
U.S. Pat. No. 4,011,130 to Worden discloses waterlaid sheets comprising essential solids consisting of (I) elastomeric (polyurethane) binder, and (II) nonelastomeric solids comprising inflexible, non-fibrous, rounded, particulate fillers (which may be vegetable flours prepared from peach pits, apricot pits and cherry pits) and a fibrous reinforcing component. The waterlaid sheets are useful as substitutes for leather in the manufacture of footwear, particularly as the outsole or insole portion of a shoe. However, no comparison of tensile strength between the neat polymer and the polymer composite is provided.
Accordingly, polymer and plastic industries would benefit from a demonstration of affordable, efficient bio-fillers which would reduce the cost of the final products and yet not diminish the strength characteristics of the polymer, as compared to the corresponding non-composited polymer.